(1) Field of the Invention
The present invention relates to a lubricant molded body to be applied onto a surface of a photosensitive layer for electrophotograph, a lubricant application apparatus to apply the lubricant of the lubricant molded body to the surface of the photosensitive layer for the electrophotograph, a process cartridge equipped with the lubricant application apparatus, and an image forming apparatus equipped with the lubricant application apparatus.
(2) Related Art Statement
To improve the cleaning power of the electrophotography apparatus used with the copier or the like, a technique is proposed, which applies a higher fatty acid metallic salt (metallic soap) to an image carrier or an intermediate transfer belt as a lubricant or cleaning adjuvant. This higher fatty acid metallic salt chiefly indicates higher fatty acid salts of metals: alkaline earth metals. The higher fatty acid metallic salt has the structure in which a non-polar part based on the higher fatty acid part is combined with a polar part based on the metal portion. The polar parts gather together due to electrostatic force, while the non-polar parts are rubbed together to exhibit high lubricity.
When such a higher fatty acid metallic salt is applied to the image carrier or the intermediate transfer belt, adhesion of the developer to the image carrier or the intermediate transfer belt decreases. In addition, since the higher fatty acid metallic salt agglomerates to the surface of the image carrier or the intermediate transfer belt as nuclei, the cleaning power for the image carrier and the intermediate transcript belt is improved. Furthermore, because the depth of wearing of the image carrier decreases, the use life of the image carrier becomes longer.
As a coating system of the higher fatty acid metallic salt, there is employed a system in which a block-shaped lubricant molded body formed from the higher fatty acid metallic salt is shaved off with a brush or the like, and resulting shaved pieces in the form of fine powder are coated. Such a coating system is advantageous from the viewpoint of saved space, quantitative and uniformity application, and control on the applied amount.
FIG. 4 is a schematic explanation view of a conventional lubricant application apparatus. In FIG. 4, 101 is a lubricant molded body, 102 is a planar support, and 103 is a brush roller. The lubricant molded body 101 has a rectangular parallelepiped block shape with a large aspect ratio. Such a lubricant molded body 101 is fixed on the planar support 102. The surface of the lubricant molded body is shaved off with a brush roller 103 that is rotated on the surface of the molded body, and the finely powdery higher fatty acid metallic salt that is adhered to the brush roller 103 is transferred and uniformly applied onto the image carrier (See “1” in FIG. 3) and the intermediate transfer belt (See “6b” in FIG. 3) arranged at respective positions contacting with the brush roller 103. The lubricant molded body 101 may be directly contacted to the image carrier or the intermediate transfer belt without the brush roller 103 placed, depending upon the construction.
FIG. 5 shows a conventional molding die to form lubricant molded bodies, FIGS. 5(A), 5(B) and 5(C) being a plan view, and a sectional view along a line B-B and a sectional view along a line C-C in FIG. 5(A), respectively. The conventional molding die that forms the lubricant molded bodies has a split mold structure. The molding die consists of three split die portions: a middle die portion 104 being planar, an upper die portion 105 having an arbitrary number of bar-shaped cavities 107 corresponding to molded bodies to be molded, and a lower die portion 106 also having an arbitrary number of bar-shaped cavities 107 corresponding to molded bodies to be molded. The length of the cavity 107 is made longer than that of the desired lubricant molded body.
When such a molding die is to be used, the upper portion 105, the middle die portion 104 and the lower mold die portion 106 are fastened by an arbitrary means and preheated, and then the higher fatty acid metallic salt is melted by heating, and then charged into the cavities 107. The charged salt is spontaneously cooled to solidify the higher fatty acid metallic salt. As the higher fatty acid metallic salt that forms lubricant molded body 101, compounds such as zinc stearate, calcium stearate, barium stearate, aluminum stearate, zinc laurate, calcium laurate, etc. are recited. The lubricant molded body 101 is obtained through heating and melting the higher fatty acid metallic salt in a highly powdery state, pouring the melt in the molding die with the cavities each having a desired shape, and solidifying the thus melted higher fatty acid metallic salt by cooling.
However, the shrinkage of the higher fatty acid metallic salt is large at the time of solidification in cooling. Consequently, particularly when the higher fatty acid metallic salt was molded as a lubricant molded body having a rod-like shape with a large aspect ratio, there was a problem that the molded body was likely to be cracked or cut at the time of solidification in cooling.
In view of this, there is proposed a technique (JP7-26278A now patented under Japanese Patent No. 2,796,486) that cracking and cutting are prevented by solidifying the melted higher fatty acid metallic salt within the molding die by cooling successively from a lower portion to an upper portion. This technique opened a way to enable the mass production of rod-shaped lubricant molded bodies. However, since it is necessary to effect cooling for a long time period so as to avoid rapid shrinkage at the time of solidification in cooling, the number of metal molding dies must be increased to raise the production amount. Therefore, there was a problem that the initial investment cost increased.
Moreover, a technology was proposed, which decreased cracking and cutting of the molded bodies on molding by alleviating the strain due to shrinkage through providing an appropriate space to the metal mold (See JP10-279998A). However, there was also a problem in this technology that it was necessary to monitor the cooling temperature carefully.